Information rate accelerator and decelerator or the like



INFERMATION RATE ACCELERATOR AND DECELERATOR OR THE LIKE Filed Oct. 24, 1955 Jan. 28, 1958 I L R. JACOBSEN ET AL 2,821,654

42 I l m lO'mSECJI L L I it? A READING GATE WRITING GATE BI-STABLE Bl-STABLE 38 SWITCH SWITCH 'r iooomsec. T=lOrmSEC.

SQUARE PULSE GENERATOR Bl-STABLE SWITCH AND AMPLIFIER ACCELERATED FREQUENCY ,35

LANCE R. JACOBSEN THEODORE a. woop RS THEIR' ATTORNEY United States Patent 1;

INFORMATION RATE ACCELERATOR AND DECELERATOR OR THE LIKE Lance R. Jacobsen, Lynwood, and Theodore B. Wood, Burbank, Calif., assignors to Hotfman Electronics Corporation, a corporation of California Application October 24, 1955, Serial No. 542,399

2 Claims. (Cl. 315-12) This invention is related to multiplex systems and, more particularly, to the accomplishment of multi-channel transmission and reception by time sharing means.

This invention makes use of storage tubes, as they are called, and the principles of operation thereof. A storage tube may be defined as a cathode ray tube containing a surface which may be charged by an electron beam to provide a record of information over the length of a single sweep or an entire scan, and which may later be discharged to obtain the stored information in the form of voltage variations. There are in existence two general types of storage tubes. The first type includes the Iconoscope and Orthicon varieties which are employed generally in television pick-up equipment. In these tubes the storage surface is charged by the electron beam, and

the charge over the storage surface is modified by photoelectric emission. The most satisfactory photo emitters are metals or semiconductors. Hence, the storage surface, in being a metal or semiconductor, must be broken into a mosaic of photosensitive particles to prevent conduction across the surface. In the second type of storage tube photo-emission plays no part. The metallic or semiconductor mosaic is therefore unnecessary and hence the storage surface consists only of a plate of uniform, highly insulating material. The only requirements imposed upon this material are the condition that it must emit more than one secondary electron for each primary electron striking it, and that it must have extremely high resistivity. A very recent development has been a storage tube resembling somewhat the Orthicon variety, so far as the target mosaic is concerned, in which a conductor or semiconductor storage surface is employed, and in which two electron guns and a secondary electron collector or collectors are employed. Very recent developments of the tube have included in the storage portion a composite side of the aluminum foil. The first electron gun, or

writing gun, faces the mesh supporting the alumnium foil, whereas the second, or reading electron gun, faces the magnesium floride target. In principle of operation, the high energy electron beam of the writing gun is modulated by an input signal and scans and penetrates the aluminum foil to charge the magnesium floride target mosaic. When the writing scan is completed, the writing gun is cut ofi, and the reading gun scans the target so as to convert the stored signal into voltage fluctuations across an output impedance. Suppose now, for example, that the writing and reading electron gun were connected to a bistable switching circuit so that one gun is cut E while the other gun is conducting, and further, that the reading gun scans the storage area at a much faster rate than the writing gun in initially impressing the target area with the energy to be stored. In such event, the input signal frequencies would be multiplied in proportion to the ratio 2,821,654 Patented Jan. 28, 1958 of the reading scan time interval to the Writing scan time interval. If this ratio is high enough, the writing gun may be cut oif for only a negligible amount of time with respect to its scanning frequency or frequencies so that substantially all of the input information will be stored on the target area, sequentially, to be taken off as electrical voltage fluctuations by the reading gun during the short, intermittent reading intervals. It follows that the resultant accelerated signal frequencies may be used to modulate a carrier in a multiplex or multi-channel transmission system with the difference in scanning time between the reading gun and the writing gun being timeshared by the remainder of the channels employed.

Therefore, it is an object of the present invention to provide a new and useful signal accelerator and decelerator system for employment in multiplex systems.

It is a further object of the present invention to provide a suitable means for a system which by time sharing techniques will render possible multiplex operation with a minimum of cost of equipment.

According to the present invention, an information signal modulates the high energy electron beams of the writing gun of a storage tube. The stored information is scanned by a reading electron gun at a much faster rate than the writing scan previously accomplished. Bistable switch means simultaneously opens the writing gate circuit associated with the writing electron gun and closes the gate circuit associated with the reading electron gun and alternatively reverses this operation in selected sequence. The output signal taken from the reading gun circuit is compressed tirnewise though multiplied in frequency by a factor inversely proportional to the ratio of the time of scan of the reading gun to the time of scan of the writing gun. Hence, although the band width of the output signal is materially widened, yet for only a small portion of the time cycle will transmission be effected; hence, time sharing by other channels in a multiplex system is made possible.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawing, in which:

The sole figure is a schematic diagram partially in block form of a signal accelerator and decelerator circuit according to the present invention.

In the sole figure input signal terminals and 11 are coupled through an input amplifier 12 to bistable switch 13. Bistable switch 13 serves as a writing gate and is triggered by output pulses from generator 14. Output terminal 15 of switch 13 is directly connected to cathode 16 of electron gun 17. Output terminal 18 of switch 13 is coupled to the negative side of battery 19, or other equivalent voltage source, and also through input resistor 20 to control grid 21. Control grid 21 is also coupled through coupling capacitor 22 to input amplifier 12, as shown. The positive side of battery 23, or other equivalent voltage source, as well as the positive side of battery 19 is coupled to ground and to secondary electron collector 24 of storage tube 25. Collector 26 is coupled to ground, and to the positive side of battery 27. The negative side of battery 27 is coupled through capacitor 28 to collector 26, through resistor 29 to aluminum foil 30 of storage portion or target area 31, and through capacitor 32 as shown to bistable switch and amplifier 33. Input amplifier 12 is coupled to bistable switch amplifier 33 from which the accelerated signals are taken at terminals 34 and 35. The target area 31 itself is composed of an insulating portion 36, conducting portion or foil 30, and

wire mesh supporting portion 37. Bistable switch 38 is intercoupled with bistable switch 13 and with switch and amplifier 33. Terminals 39 and 40 of bistable switch 38 are coupled to cathode 41 of reading gun 42 and to the negative side of battery 23, respectively. Accelerating anodes and 44 of the two electron guns may be maintained at ground potential if desired. Each electron gun is provided with aseparate defiection system (systems 45 and 46) which are shown generically merely in a dotted line configuration.

The circuit shown in the sole figure operates as follows. The general operation of the storage tube 25 has been heretofore explained. The design of generator 14 and of the various bistable switches is such that the writing gate, bistable switch 13, will be open for a comparatively long period of time whereas the reading gate, bistable switch 38, and bistable switch and amplifier 33 will be open for a relatively short period of time immediately following the opening of bistable switch 13. Suppose for example that the writing gate bistable switch is open for 1,000 milliseconds, which opening is caused by the occurrence of control pulses from pulse generator 14. Suppose also that, following the opening of bistable switch 13 for 1,000 milliseconds that bistable switch 33 is subse quently opened for 10 milliseconds, as will also be bistable switch and amplifier 33. In such a case, upon the opening of bistable switch 13, the signals impressed upon input terminals 10 and 11 are translated through input amplifier 12 and through writing gate bistable switch 13 to the input of electron writing gun 17 of storage tube 25 across input resistor 20. Deflection system 4-5 will provide for the complete scan of target 31 during the 1,000 millisecond interval so that, upon the termination of this time interval the signal energies for that interval will be stored over a chosen portion of target area 31 of storage tube 25. During this 1,000 millisecond interval, bistable switch 38 will remain closed, as will bistable switch and amplifier 33. After the energy is stored on target area 31 by virtue of deflection system 45 completing its scan, then writing gate bistable switch 13 will become closed and bistable switch 38 and bistable switch and amplifier 33 will be open. During the brief opening of these two bistable switches, the deflection system 46 for electron gun 42 will complete a short, quick scan of target area 31 which will result in a production of voltage fluctuations across output resistor 29 corresponding to the input signal in amplitude but multiplied in frequency components. This output signal from the storage tube is immediately fed through capacitor 32 and through bistable switch and amplifier 3-3 which is now open to output terminals 34 and 35. it is seen, then, that by the apparatus shown and described the signal will undergo a time compression, that is, will be reduced from a 1,000 millisecond duration to a 10 millisecond duration. However, the sev eral component frequencies will all be multiplied by a factor equal to the ratio between the scanning speed of deflection system 46 and the scanning speed of deflection system 45. After the 10 millisecond interval the readin gate bistable switch 38 and bistable switch and amplifier 33 will be closed and writing gate bistable switch 13 will again be opened by the output signal from square pulse generator 14.

The terminal voltage of battery 19 should be approximately 10,000 volts, which will combine with the accelerating anode of electron writing gun 17 to give the writing electron beam sufficient energy to penetrate aluminum foil 30 and thus impinge upon target 31. A voltage of similar magnitude should likewise appear across the terminals of battery 23, so as to accomplish the reading of the stored information in target 31. By battery source 27, a positive voltage of approximately 50 volts is applied between aluminum foil 3!) and collector 26 which, in reality, is imposed across the front and back faces of target 36 during intervals of secondary emission so that the target mosaic may undergo charge modulation during the writing beam scan.

it is accordingly seen that the above system as shown at described illustrates a time compression of a given :tll signal by novel signal acceleration and deceleration means through the employment of an appropriate storage tube.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

We claim:

1. In combination, a storage tube having a writing gun, a reading gun, a storage portion, a writing gun deflection means, and a reading gun deflection means; a first input circuit coupled to said writing gun; a second input circuit coupled to said reading gun; a first deflection system means coupled to said Writing gun deflection means for impressing a complete voltage scan upon said writing gun deflection means over a chosen first time period; a second deflection system means coupled to said writing gun defiection means for impressing a complete voltage scan upon said writing gun deflection means over a chosen second time period shorter than and following said first time period; an output impedance coupled to said storage portion of said storage tube; a bistable electronic switch means coupled to said first and second input circuits for simultaneously opening said first input circuit and closing said second input circuit over said first time period and, subsequently, simultaneously closing said first input circuit and opening said second input circuit over said second time period; an output circuit; closeable circuit means coupled to said bistable electronic switch means and electrically interposed between said output impedance and said output circuit for selectively passing output signals from said storage tube during said second time period; and a signal source coupled through at least a portion of said bistable switch means to said first input circuit of said electron writing gun.

2. Apparatus according to claim 1 in which said storage tube includes at least one secondary electron collector, and in which a voltage source is coupled between said storage portion and said secondary electron collector.

Baker Sept. 13, 1955 Roschke June 26, 1956 

